1. Field of the Invention
This invention relates to a transimssion chain assembly suitable for use on vehicular transmissions or as power transmission means for industrial machines in general.
2. Description of the Prior Art
Conventional power transmission chains are generally composed of a series of articular units each consisting of a number of interleaved links of the same shape which are provided with a pair of apertures at a predetermined interval and pivotally connected to links of adjacent units by pins inserted in the apertures for articulation in the longitudinal direction. Therefore, when a claim of this type is engaged with a sprocket with uniformly spaced teeth, the respective articular units of the chain repeatedly make noises upon engagement with a sprocket tooth, which is called "tooth contact noises". As is well known in the art, the tooth contact noises which are annoying to the ear are produced by the engagement of the chain links with the sprocket teeth, and determined by the number N of the sprocket teeth and the number of revolutions R (rpm) of the sprocket, the noises containing an abnormally high-level component at the tooth contact frequency per second of N.times.R/60 (Hz).
An attempt to reduce such tooth contact noises is described in U.S. Pat. No. 4,342,560 in which a chain is constructed with two types of links, i.e., outside engagement type links and inside engagement type links. These two types of linkes are incorporated into a chain in either (1) an alternate pattern or (2) a pattern of random mixture. In this regard, Japanese Laid-Open Patent Application No. 60-188639 discloses a chain which is constructed with two types of links as shown in FIG. 6, namely, an outside engagement type link A which engages the sprocket teeth on its outer flank surface 21 and an inside engagement type link B which engages the sprocket teeth on its inner flank surface 22, forming a chain by repeating a link arrangement pattern of mixing more than three links of a different type.
In both of the prior art chains described above, the discomfortable noises are reduced by altering the basic frequency of the tooth contact noises of the chain and sprocket or the resonant frequency with respect to surrounding objects, with a view to dispersing the peak values of the noise.
However, in any case the conventional chain requires providing links of at least two different types, that is to say, links of inside engagement type and links of outside engagement type.
On the other hand, recently the technology for industrial machines or similar products has a trend toward lightweight and compactness, and the same applies to power transmission chains. In order to meet such a demand, it is effective to minimize the radius of the sprocket with which the chain engages, and reducing the number of sprocket teeth to minimize the radius of rotation of the chain. However, on a smaller sprocket, the chain links have a greater angle of flexion .delta. as shown in FIG. 3(b).
As shown in FIGS. 4(a) and 4(b), bulged or curved portions 32 and 32' are provided on the inner flanks which define crotch portions of inside engagement type links of the conventional chain, which engages the sprocket teeth on the side of the crotch portions. These bulged portions 32 and 32' are provided for the purpose of lessening the chordal actions, the cause of vibrations and noises, which occur to the chain as a result of fluctuations in speed caused by flexions at the time of engagement with the sprocket teeth. This is the same purpose as that of the chain links with a couple of roll pins. However, in case of a chain having the bulged portions on the inner flanks which define the crotch portion of each link, its angle of flexion .delta. becomes greater on a sprocket with a reduced number of teeth and therefore it becomes necessary to bulge out the inner flank portions to a greater degree to produce their effect sufficiently from an initial point to a to final point of engagement with a sprocket tooth. Consequently, larger bulged portions have to be provided on the inner flank portions of the chain links.
However, in the case where the inner flank portions are bulged out in to a greater degree, there arises a problem in that the engagement of one bulged portion 32 with a sprocket tooth 33 is interfered with by the other bulged portion 32' on the opposite side of the tooth, making normal engagement with the sprocket difficult.
A reduction of the in thickness of the sprocket teeth is conceivable as means for solving the just-mentioned problem, but it has a drawback in that the strength of the sprocket has to be sacrificed.